xnestWindowExposures() is a micro-optimization for the specific case that
a newly created window receives exposure events (from our upstream server)
inside the region we're already exposing on our own (miWindowExposures()):
it peeks the Xlib event queue for all expose events, checks whether their
areas are inside our exposure region and requeue's those that aren't.
Unfortunately, this depends on Xlib's internal queue mechamism, thus standing
in the way of moving to XCB (which doesn't have that).
Removing this doens't seem to make any practical difference, even with
demanding applications like GIMP. The only cost is potentially having some
initial window content painted twice, *if* the application really draws
something complicated right after creating the window.
*If* there'll really be a demand for such an optimization some day, it can
be reimplemented without any message queue: just redirecting all expose events
into recording them in a region, which is flushed out later. But for now,
there really doesn't seem to be any practical need for that.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
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